It has been known to employ an angle sensor for detecting a valve opening degree of an electrically operated valve.
As a relevant technique, a valve opening degree detecting device of an electrically operated valve is disclosed in patent document 1. The valve opening degree detecting device described in the patent document 1 is provided with a magnetic drum in which N poles and S poles fixed to a rotating shaft are circumferentially magnetized in a uniformly divided manner, a magnetic sensor for detecting an angle of rotation which is provided on a circumference outside a can facing the N and S poles, a magnet which is provided in an end portion of the rotating shaft, a magnetic sensor for detecting a vertical position which is provided outside the can facing the magnet, and a valve opening degree computing means which computes a valve opening degree on the basis of detected values of the magnetic sensor for detecting the angle of rotation and the magnetic sensor for detecting the vertical position.
Further, an electrically operated valve using a stepping motor is disclosed in patent document 2. The electrically operated valve described in the patent document 2 is provided with a stator, a rotor which is rotationally driven by the stator, a detection rotor which detects a rotational position of the rotor, and a Hall IC which is arranged outside the detection rotor. In the electrically operated valve described in the patent document 2, the rotational position of the rotor is detected on the basis of an output signal which is detected by the Hall IC arranged outside the detection rotor.